ISO 9416 is a standard on the determination of light scattering and absorption coefficients for paper, using the Kubelka-Munk theory. The standard specifies a calculation method for light scattering and absorption coefficients based on diffuse reflection measurement, which is suitable for white and near-white unSpreader paper or Cardboard and pulp with less than 95% opacity. The test uses CIE light source C and Color matching function to calculate light scattering and absorption coefficients through UV-VIS-NIR spectrophotometer measurement reflectance and transmittance. This method provides a simple and reliable calculation method for the evaluation of paper and pulp Optical inspection characteristics, and is widely used in quality control and Product Research & Development in the paper industry.